Add SDK observability hooks design

[El-swaggerito]

Description

Difficulty: Expert

Type: Feature

Summary

Design safe observability hooks for SDK consumers to track non-sensitive operation progress.

Current Behaviour

Consumers may need progress events for payments and vault actions, but logging sensitive data is risky.

Expected Behaviour

The SDK should expose safe lifecycle events without leaking secrets.

Suggested Implementation

Design hooks for transaction stages, network calls, retries, and final outcomes with redaction rules.

Files or Areas Likely Affected

src/transactions/
src/network/
src/types/
docs/

Acceptance Criteria

• Observability hook design is added.
• Events avoid sensitive data.
• Transaction lifecycle stages are covered.
• Redaction rules are documented.
• Examples show consumer usage.

Additional Notes

This should not become verbose logging by default.

[Mubking-dev]

Hi, I'm Mubarak — a Full-Stack & Blockchain Developer with 3+ years of experience. I've reviewed this issue and I'm confident I can handle it. I'll submit a clean PR within 2–3 days. Please assign it to me!

[grantfox-oss]

🦊 GrantFox — @Mubking-dev has been assigned to this issue as part of the Official Campaign | FWC26 campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #222)
2. Your PR will be reviewed by the Axionvera maintainers

Good luck! Track your progress on GrantFox.